138 ON NERVE-EXCITATION BY THE NERVE-CURRENT. 



I have already mentioned that the land-frogs which I used 

 showed much less disposition to tetanus after nerve-section than 

 did water-frogs. I, however, obtained from the former also 

 strong closure or opening tetanus by excitation of the transverse 

 section. 



Pfliiger l has attempted to explain the great disposition of frogs 

 brought from a cold to a warm place to fall into a tetanic state, by 

 some 'transposition of atoms' brought about by the influence of 

 warmth. But without any desire to call in question the influence 

 of warmth on a preparation, I must mention that frogs which had 

 been kept in a cold room gave a tetanus of the corresponding limb 

 after section of the sciatic plexus, even when the section was made 

 in the same cold room and with cold scissors, so that any warming 

 of the preparation was out of the question. They also reacted 

 tetanically to weak battery-currents. 



The tetanus consequent upon nerve section can be completely 

 arrested, or, at any rate, much diminished, by weak ascending 

 currents, if one electrode is applied to the transverse section, and 

 the other to a neighbouring point of the longitudinal section. It 

 recommences, however, when the current is broken. A strong 

 muscle-current suffices to arrest it. If I placed the recently cut 

 nerve between two muscles possessing a transverse section, in such 

 a way that the transverse sections of the nerve and of both muscles 

 lay in the same plane, I observed that the tetanus forthwith 

 diminished or entirely disappeared, reappearing after removal of 

 the muscles. Thus it happens that, even with the most excitable 

 frogs, the tetanus is generally absent if the whole thigh is severed 

 at one blow of the scissors, because the currents of the cut muscles 

 forthwith act upon the cut nerve. 



If the sciatic nerve on one side is laid bare, and divided after 

 careful isolation from the muscles, the leg, if the preparation is 

 a sensitive one, becomes tetanised ; while an incision on the other 

 side, and at the same level, but passing through the nerve and all the 

 muscles, causes a contraction of the leg only during the operation, 

 and is followed by complete relaxation. If after section of the sciatic 

 plexus a strong tetanus should have supervened in the leg of that 

 side, it is at once abolished by sudden amputation through the 

 thigh ; but if thereafter the two branches of the sciatic nerve 

 above the knee are divided, tetanic agitation of the leg reappears. 



1 Untersuch. iiber die Physiol. des Elektrotonus, p. 133, 1859. 



